Compressed natural gas (CNG) is a high octane fuel that is beneficial for reducing engine knock, hydrocarbon emissions in cold start events, and carbon dioxide emissions during engine operation. However, CNG has a low energy density compared to liquid hydrocarbon fuels, such as diesel fuel or gasoline. To increase the range and total fuel quantity stored in a vehicle, CNG may be utilized in conjunction with gasoline or diesel fuel, requiring the vehicle to switch between fuels for optimal performance. To facilitate the consumption of both gaseous and liquid fuels, two separate fuel tanks may be included in the vehicle to store the gaseous and liquid fuels, respectively.
The inventors herein have recognized several issues with the above approach. Namely, the use of two separate fuel tanks that respectively store gaseous and liquid fuels increases vehicle weight, packaging space, complexity of fuel storage and injection, and reduces fuel economy. These issues are exacerbated for light duty vehicles.
One approach that at least partially addresses the above issues includes a method of refueling comprising supplying a liquid fuel to a fuel tank configured to store both the liquid fuel and a gaseous fuel, if a pressure in the fuel tank is less than a threshold pressure.
In a more specific example, liquid fuel is supplied to the fuel tank if the liquid fuel is sensed in a surge tank configured to store the liquid fuel, the surge tank fluidly coupled to the fuel tank and positioned upstream of the fuel tank.
In another aspect of the example, vapor from the fuel tank is pumped to a secondary tank if the pressure in the fuel tank is greater than the threshold pressure.
In this way, a vehicle may be supplied and refueled with two different fuels by using a single fuel tank to store the fuels, reducing vehicle weight, packaging space, complexity of fuel storage and injection, and increasing fuel economy. Thus, the technical result is achieved by these actions.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.